Double-resonance spectroscopy of the high Rydberg states of HCO. V. Rovibronic interactions and l-uncoupling in the (010) manifold

We report the ionization-detected absorption spectra of autoionizing Rydber g states converging to the (010) vibrational level of HCO+. Sharp second-ph oton resonances appear in transitions from first-photon-prepared originatin g states that have total angular momentum (less-spin) from N'=0 to 5, selec ted from the Sigma(+) and Sigma(-) components of the (010) band of the 3p p i(2)Pi Rydberg state. We systematically compare spectra in order to charact erize observed resonances in terms of the good total angular momentum quant um number, N. Rydberg analysis establishes the convergence of series to det ailed cation-core rotational quantum numbers, N+. Observed series are found to fit well with simulations employing a limited set of constant quantum d efects (delta=1.062, 0.794, 0.606, 0.253, 0.015, 0.002, -0.027 and -0.076). The strengths of observed transitions as a function of initial and final t otal angular momentum provide a purely experimental indication of the appro priate assignment of the approximately good orbital angular momentum quantu m number, l, for each series. Interactions between Rydberg orbital and core rotational angular momentum are found to conform with a coupling case inte rmediate between Hund's cases (b) and (d). Splitting patterns further assig n certain features according to predominant case (b) composition. (C) 2000 American Institute of Physics. [S0021-9606(00)00637-1].